Hose clamps are used to seal the connection between a hose or other cylindrical conduit and a cylindrical nipple. The clamps encircle the hose and apply a radially inward directed compressive force to cause the hose to form an elastomeric seal with the nipple.
Various types of hose clamps are employed. One of the more prevalent types has a band which extends about the portion of the circumference of the hose. A "T" bolt extends across the remaining portion . The ends of the band form retaining loops, and the "T" bolt has a "T" end which is retained in one of the retaining loops and a bolt shank which extends through the trunnion which is retained in the loop on the other end of the band. A nut is placed on a threaded end of the bolt shank. Tightening the nut forces the ends of the band toward each other which applies tensile force to the band, thereby causing the hose clamp to apply the compressive force on the hose.
One of the drawbacks of the "T" bolt type of hose clamp is what is referred to as a "cold-leak". Cold Leak is a condition brought about by the thermal cycle of the system. Initially, the system is at ambient temperature. As system temperature increases to normal operating temperature, thermal expansion of the nipple may be greater than the thermal expansion of the hose clamps. This difference in thermal expansion may cause an increase in the compressive forces applied to the hose material with a resulting displacement of the material. When the system is shut down and returns to ambient temperature, the thermal contraction of the nipple may exceed thermal contraction of the hose clamps. This difference in thermal contraction may reduce the compressive force applied to the hose to a level less than required to maintain a seal between the hose and nipple, resulting in Cold Leak.
To overcome the drawbacks of cold-leak, certain prior art devices employ a spring which circumscribes the bolt shank of the "T" bolt. The spring applies an outward directed biasing force on the nut on the end of the shank and an opposite biasing force on the trunnion end of the band through which the "T" bolt shank extends. The opposite biasing forces draw the ends of the band together.
When the hose clamp is initially installed, the springs are compressed. During cold weather and as a nipple contracts, the spring compensates for the contraction by increasing in length while continuing to exert the opposing forces on the "T" bolt and trunnion. Such hose clamps are sometimes referred to a self-tightening clamps.
One method to cause the hose clamp to supply a higher compressive force between the hose and the nipple, is to reduce the width of the band while maintain the same tensile force. The decrease in band width while applying the same total tensile force increases the force per unit area exerted on the hose and nipple. In addition, frequently space requirements necessitate a narrow hose clamp while maintaining the same compressive force. However, with the "T" bolt clamp, to decrease the width of the band, the "T" bolt must also be reduced in size.
One of the drawbacks of using a spring self-tightening clamp when reducing the size of the band is that the spring needs to be of a certain size and circumference to exert the proper total compressive force on the hose nipple connection. Thus, the spring must be maintained at a minimum size. However, upon decreasing the size of the "T" bolt to reduce the width of the band while maintaining the size of the spring, the spring may become off centered about the bolt. An off centered spring can bind or exert a non-uniform force on the band which lessens the effectiveness of the self-tightening feature.
It is therefore an object of the present invention to provide a clamping device for forcing a hose into a sealing engagement with an underlying hose, nipple or the like.
Another object of the present invention is to provide a clamping device which seals the connection between a hose and compensates for small variations in the diameter of a hose.
Yet another object of the present invention is to provide a clamping device which utilizes a spring like biasing element and a "T"-bolt feature to self-tighten the clamp. A related object is to provide such a device which maintains the biasing element centered about the bolt.